Field of the Invention
The present invention relates to a feeding apparatus and a printing apparatus, and more specifically to a feeding mechanism that separates and feeds sheets one by one using a separation surface.
Description of the Related Art
As a feeding mechanism that separates sheets using a separation surface, the feeding mechanism is known that uses two separation surfaces such as disclosed in Japanese Patent No. 3501714. The feeding mechanism that is disclosed in Japanese Patent No. 3501714 is such that the separation surface comprises a first separation surface, and a second separation surface that has a higher friction coefficient than the first separation surface, and is provided so as to be able to move along the first separation surface and in the direction of movement of a sheet that is output by a feed roller. By providing the second separation surface so as to be able to move, it becomes possible to feed sheets without deforming a sheet regardless of the stiffness of the sheet such as whether the sheet is thin or thick. Moreover, the second separation surface is able to prevent overlap feeding of sheets by an operation of returning to the upstream side by the elastic force of spring.
However, when applying the feeding mechanism disclosed in Japanese Patent No. 3501714 to a so-called auto-sheet feeder in which the sheet mounting surface of a sheet stacking device makes a comparatively large angle with respect to horizontal, and sheets are set so as to be inclined downward from the top, there are the following problems.
For example, when the elastic force of the spring that return the second separation surface to the upstream side is relatively weak, the second separation surface may move toward the downstream side due to the weight of plural sheets that are set on the sheet-mounting surface and due to the stiffness of the sheets. When the top sheet is separated and fed in such conditions, the front-end section of sheets other than the top sheet may become deformed along the separation surface due to the movement of the second separation surface, and the balance between the elastic force of the springs and the force acted by the sheets may be lost, resulting in only the second separation surface returning to the upstream side. As a result, the front ends of the sheets may drop further toward the downstream side than the second separation surface, the breaking force created by the high friction coefficient of the second separation surface may be lost and overlap feeding of sheets may occur. In contrast, when the elastic force of the spring is relatively large, for example, the second separation surface becomes unable to move and then may be unable to feed sheets or may damage the front ends of the sheets in the case of feeding sheets in a state of a small number of sheets stacked.
When various kinds of sheets having various thicknesses are set on the sheet-mounting surface, it is difficult to eliminate the problems related to sheet feeding through the second separation surface by adjusting the elastic force of the spring that return the second separation surface to the upstream side.